Such a system may for example be formed by the following scenarios:                system for remote inquiry of electricity meter readings over the power line or the power supply network,        database server with accesses via clients        client/server configuration comprising internal data exchange        remote setting of devices        remote inquiry of account balances        system in a vehicle having networked processors/microcontrollers, in particular motor control, alarm system or central door safety system,        etc.        
Symmetric and asymmetric encryption methods are generally known, wherein a safe message channel between communication parties is formed. Further, symmetric and asymmetric methods, like for example a digital signature or a message authentication code (MAC) are generally used, wherein the authenticity and/or integrity of a message, a party, or a key may be tested by a reception unit. General basics are for example described in the book “Kryptographie” by W. Fumy and H. P. Rieβ, “Entwurf und Analyse symmetrischer Kryptosysteme”, R. Oldenburg Verlag Munchen, Wien, 1988.